Add list proxy

Author: peterbrittain

CHANGES.rst

@@ -10,6 +10,7 @@ LATEST
 - Added mouse scroll wheel support.
 - Added reset() to Renderers.
 - Added type hints to source code.
+- Textbox value now supports list methods - e.g. `TextBox.value.append("foo")` will change the value.
 - Fixed double-width alignment issues on DropdownList.
 - Improved TextBox line wrapping to break on word boundaries.
 - Fixed logic for highlighting selected widget controls without focus.

asciimatics/widgets/filebrowser.py

@@ -145,11 +145,9 @@ def _populate_list(self, value: str):
                     name = f"|-- {my_file} -> {real_path}"
 
             # Normalize names for MacOS and then add to the list.
-            tree.append(([
-                unicodedata.normalize("NFC", name),
-                readable_mem(details.st_size),
-                readable_timestamp(details.st_mtime)
-            ],
+            tree.append(([unicodedata.normalize("NFC", name),
+                          readable_mem(details.st_size),
+                          readable_timestamp(details.st_mtime)],
                          full_path))
 
         tree_view.extend(sorted(tree_dirs))

asciimatics/widgets/textbox.py

@@ -1,8 +1,10 @@
 """This module implements a multi line editing text box"""
 from __future__ import annotations
 from copy import copy
+from functools import partial
 from logging import getLogger
 from typing import TYPE_CHECKING, Callable, List, Optional, Tuple, Union
+from wrapt import ObjectProxy
 from asciimatics.event import KeyboardEvent, MouseEvent, Event
 from asciimatics.screen import Screen
 from asciimatics.strings import ColouredText
@@ -15,6 +17,37 @@
 logger = getLogger(__name__)
 
 
+class _ListWrapper(ObjectProxy):  # pylint: disable=abstract-method
+    """
+    A proxy for list objects.
+
+    This class can be returned by the `value` property, allowing the caller to modify it via standard
+    list modifications.  For example, `textbox.value.append("foo")` will now update the value of the textbox.
+    """
+
+    def __init__(self, lst: List, parent: TextBox):
+        super().__init__(lst)
+        self._self_parent = parent
+
+    def append(self, stuff):
+        self._self_parent.proxy_update(partial(self.__wrapped__.append, stuff))
+
+    def extend(self, stuff):
+        self._self_parent.proxy_update(partial(self.__wrapped__.extend, stuff))
+
+    def insert(self, key, value):
+        self._self_parent.proxy_update(partial(self.__wrapped__.insert, key, value))
+
+    def __setitem__(self, key, value):
+        self._self_parent.proxy_update(partial(self.__wrapped__.__setitem__, key, value))
+
+    def __delitem__(self, key):
+        self._self_parent.proxy_update(partial(self.__wrapped__.__delitem__, key))
+
+    def clear(self):
+        self._self_parent.proxy_update(self.__wrapped__.clear)
+
+
 class TextBox(Widget):
     """
     A TextBox is a widget for multi-line text editing.
@@ -146,8 +179,10 @@ def reset(self):
         self._start_column = 0
         if self._auto_scroll or self._line > len(self._value) - 1:
             self._line = len(self._value) - 1
-
-        self._column = 0 if self._is_disabled else len(self._value[self._line])
+        try:
+            self._column = 0 if self._is_disabled else len(self._value[self._line])
+        except IndexError:
+            self._column = 0
         self._reflowed_text_cache = None
 
     def _change_line(self, delta: int):
@@ -347,10 +382,13 @@ def auto_scroll(self, new_value):
     def value(self):
         """
         The current value for this TextBox.
+
+        NOTE: this now uses a proxy to allow insertion and other modifications.
         """
         if self._value is None:
             self._value = [""]
-        return "\n".join([str(x) for x in self._value]) if self._as_string else self._value
+        return "\n".join([str(x)
+                          for x in self._value]) if self._as_string else _ListWrapper(self._value, self)
 
     @value.setter
     def value(self, new_value):
@@ -360,8 +398,23 @@ def value(self, new_value):
             new_value = [""]
         elif self._as_string:
             new_value = new_value.split("\n")
+        elif isinstance(new_value, _ListWrapper):
+            new_value = new_value.__wrapped__
         self._value = new_value
+        self._handle_changes(old_value)
+
+    def proxy_update(self, make_update):
+        """
+        Handle an update from the proxy value property object.
+
+        This is an internal method that processes potential updates to the value of the TextBox.  It
+        should never be called directly by an application.
+        """
+        old_value = list(self._value)
+        make_update()
+        self._handle_changes(old_value)
 
+    def _handle_changes(self, old_value):
         # TODO: Sort out speed of this code
         if self._parser:
             new_value = []

mypy.ini

@@ -2,6 +2,9 @@
 packages = asciimatics
 check_untyped_defs = True
 
+[mypy-wrapt.*]
+ignore_missing_imports = True
+
 [mypy-wcwidth.*]
 ignore_missing_imports = True
 

pyproject.toml

@@ -55,6 +55,7 @@ dependencies = [
         'pyfiglet >= 0.7.2',
         'Pillow >= 2.7.0',
         'wcwidth',
+	'wrapt',
 	"pywin32 >= 1.0; platform_system=='Windows'",
 ]
 requires-python = ">= 3.8"

requirements/base.txt

@@ -1,3 +1,4 @@
 wcwidth
+wrapt
 pyfiglet >= 0.7.2
 setuptools_scm

tests/test_widgets.py

@@ -3764,6 +3764,48 @@ def test_textbox_autoscroll(self):
             "|                                      |\n" +
             "+--------------------------------------+\n")
 
+    def test_textbox_proxy(self):
+        """
+        Check the list property supports normal list operators.
+        """
+        def _on_change():
+            self._new_value = [x for x in self._test_widget.value]
+
+        # Now set up the Frame ready for testing
+        self._new_value = None
+        screen = MagicMock(spec=Screen, colours=8, unicode_aware=False)
+        scene = Scene([], duration=-1)
+        canvas = Canvas(screen, 10, 40, 0, 0)
+        form = Frame(canvas, canvas.height, canvas.width)
+        layout = Layout([100])
+        form.add_layout(layout)
+        self._test_widget = textbox = TextBox(4, label="TB", on_change=_on_change)
+        textbox.value = ["Foo"]
+        layout.add_widget(textbox)
+        form.fix()
+        scene.add_effect(form)
+        scene.reset()
+
+        # Check returned list proxies updates to the form.
+        textbox.value.append("Bar")
+        self.assertEqual(textbox.value, ["Foo", "Bar"])
+        self.assertEqual(textbox.value, self._new_value)
+        textbox.value.insert(1, "World")
+        self.assertEqual(textbox.value, ["Foo", "World", "Bar"])
+        self.assertEqual(textbox.value, self._new_value)
+        textbox.value[0] = "Hello"
+        self.assertEqual(textbox.value, ["Hello", "World", "Bar"])
+        self.assertEqual(textbox.value, self._new_value)
+        del textbox.value[2]
+        self.assertEqual(textbox.value, ["Hello", "World"])
+        self.assertEqual(textbox.value, self._new_value)
+        textbox.value.extend(["Foo", "Bar"])
+        self.assertEqual(textbox.value, ["Hello", "World", "Foo", "Bar"])
+        self.assertEqual(textbox.value, self._new_value)
+        textbox.value.clear()
+        self.assertEqual(textbox.value, [])
+        self.assertEqual(textbox.value, self._new_value)
+
     def test_layout_gutters(self):
         """
         Validate that the gutters parameter works for Layouts